1. Field of the Invention
The present invention generally relates to components for use in automotive air-conditioning systems. More particularly the present invention relates to an insulated holder for use in an engine compartment of an automobile, wherein the insulated holder is designed to hold and insulate a pressure vessel of the air-conditioning system, such as an accumulator dehydrator or a receiver dryer. The overall efficiency of the vehicle air-conditioning system is significantly improved resulting in a lowering of the air temperature being blown from the ducts of the air-conditioning system within the passenger compartment of the vehicle.
2. Description of the Prior Art
One type of vehicle air-conditioning system includes a compressor, a condenser, an evaporator and an accumulator dehydrator commonly referred to as a clutch cycling orifice tube (CCOT) system. A second type of air-conditioning system has a compressor, a condenser, a receiver dryer, an evaporator and a thermostatic expansion valve (CCTXV).
In the CCOT system, the accumulator dehydrators (or accumulators) function to change liquid refrigerant fluid (which is sent to the accumulator from the evaporator) to a gaseous or vapor-laden refrigerant fluid (which is then sent to the compressor) by separating the liquid refrigerant from the gaseous refrigerant and preventing the liquid refrigerant fluid from being sent to the compressor.
In the CCTXV system, the system is designed to operate at an efficiency wherein there is only vaporous or gaseous refrigerant fluid exiting the thermostatic expansion valve (TXV) and being sent to the compressor. The receiver dryer, located after the condenser, receives a high pressure, moderate temperature liquid refrigerant fluid and functions to ensure that only liquid refrigerant is sent to the TXV.
Traditionally, the accumulator and the receiver dryer are made of a metal material having a sufficiently high strength to withstand the relatively very high pressure within the air-conditioning system. Today's accumulators and receiver dryers are more often being manufactured from aluminum and other lightweight inexpensive metal or alloy materials. However, in almost all instances the metal material has very poor insulating properties, i.e. the material is too efficient at transferring heat (in the present instance from the engine compartment to the relatively cooler refrigerant fluid located within the accumulator or receiver dryer).
In both of the above described systems, the air-conditioning system is commonly located in the engine compartment of the vehicle. Under the hood of the automobile, the engine generates a significant amount of heat. While in cold weather this is not a problem, in relatively hot weather (i.e. above approximately 80.degree. F.), temperatures under the hood of an operating vehicle, standing still, can become extremely high, as high as 250.degree. F. This heat buildup within the engine compartment can quickly affect the components of the air-conditioning system such that the temperature of the conditioned air felt at the duct outlet within the passenger compartment can begin to quickly rise. This results in the occupants of the vehicle becoming warm and uncomfortable. Thus, there is a significant problem with air-conditioning system performance during vehicle standstill conditions. The longer the vehicle stands still, the worse the problem becomes.
The prior art has addressed the problem of condensation forming on the exterior of a suction accumulator structure. For example, U.S. Pat. Nos. 3,212,289 and 5,479,790, to Bottum, Sr. and Bottum, Jr. et al. respectively, each disclose a combined receiver suction accumulator construction comprised of a pair of closed vessels arranged in spaced relation one within the other to define an air or vacuum space therebetween to prevent sweating of the inner vessel during its normal suction accumulator function. The '790 reference also discloses the use of air spaces provided around the ends of the accumulator's inlet and outlet tubes to preclude sweating or frosting. Both the '289 reference and the '790 reference disclose it is possible to circulate a relatively warm high pressure refrigerant fluid in the space between the vessels to function as a receiver and to exchange heat with the relatively cold low pressure refrigerant fluid in the accumulator. Thus, the '289 and '790 references teach the addition of heat into the accumulator.
Additionally, there is a continued problem with locating and securing the air-conditioning components, in particular the accumulator or the receiver dryer, within the engine compartment of the automobile. Due to significant space constraints and strength requirements, any mounting system must function to adequately secure the component in position. Several prior art alternatives have been proposed. For example, U.S. Pat. No. 4,888,962 discloses the use of a band clamp connected to a bracket for retaining an accumulator in position. The '962 patent discloses that the bracket can be connected within the engine compartment. The band clamp wraps around the outer periphery of the accumulator or receiver dryer and is tightened to retain the component.
One factor in determining the overall air-conditioning system performance is the efficiency of the accumulator (i.e. the ability of the accumulator to change liquid refrigerant fluid into vaporous and gaseous refrigerant fluid). Since the evaporator sends a low pressure liquid refrigerant to the accumulator, and the accumulator must send only a vaporous refrigerant fluid to the compressor, there is necessarily a pressure drop associated with the accumulator. Accordingly, the temperature at the vent outlet within the passenger compartment can be stated as a function of the temperature of the refrigerant fluid within the accumulator.
In view of the above, there have been several attempts in the prior art to provide an extremely efficient accumulator or receiver dryer that can be packaged in minimum space inside the engine compartment. It is desirable that the accumulator or receiver dryer efficiency remain unaffected by the extreme temperatures that build up inside the engine compartment, particularly during standstill traffic conditions.
The prior art has been unable to accomplish efficient operation and mounting in a minimum of space without significant structure that adds complexity and cost to air-conditioning systems. One solution has been to use the band clamp design of the '962 patent and wrap a flexible insulating material around the exposed surfaces of the accumulator, such as neoprene rubber. However, neoprene rubber degrades easily in the harsh engine compartment. Thus, there is still a need for an apparatus for mounting and insulating an accumulator or receiver dryer that increases the efficiency of the unit and, simultaneously, utilizes minimal packaging space. The apparatus should keep the accumulator or receiver dryer isolated from the effects of the engine environment, particularly during hot weather and standstill traffic conditions.